Like I said - there is more to the story than originally shared. You're talking season tickets and swapping seats. They aren't charging a donation for an accessible ticket specifically - they are charging him for the premium seating area in the stadium for the season ticket holders. It sounds like your friend is buying one class of ticket initially, and then trying to do their accessibility 'exchange' to swap to an accessible seat.
He's not being forced for a 'donation' for an accessible seat - the Stadium offers accessible seating in certain areas, and he's simply not being allowed to side-step the season ticket system by using an accessible seat. The tickets in those areas comes with the price for access to those tickets. Just like every other venue... you pay the price associated with that seat's value. The seats are not required to be the same price as any random seat in the house. You don't get free 'seat upgrades' by trying to purchase an accessible ticket.
Your whole story is predicated on the fact he's winning a lottery for one price tier, and then has to request to be moved to a higher price tier ticket. Even if they offered him to pick the accessible seat up front without the exchange... he'd still be required to pay the price of the area where the accessible seat is. Here, they've just made accessibility an exchange model instead of a 'pick up front'.
Looks like a duck - but not a duck.